USRP Hardware Driver and USRP Manual: Legacy AXI Interface Libraries

| USRP Hardware Driver and USRP Manual Version: 4.9.0.makepkg-0-g9ec1f582 UHD and USRP Manual |

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Legacy AXI Interface Libraries

This document describes legacy AXI interface libraries used by some testbenches. They are included here due to their continued use.

# AXI4 Stream (sim_axis_lib.vh)

Defines axis_t, an AXI Stream bus interface that implements several tasks to send and receive data on the bus.

## Definition

    interface axis_t #(parameter DWIDTH = 64)
                      (input clk);
      logic [DWIDTH-1:0]  tdata;
      logic               tvalid;
      logic               tlast;
      logic               tready;

    modport master (output tdata, output tvalid, output tlast, input tready);
    modport slave (input tdata, input tvalid, input tlast, output tready);

## Operations

### push_word

    // Push a word onto the AXI-Stream bus and wait for it to transfer
    // Args:
    // - word: The data to push onto the bus
    // - eop (optional): End of packet (asserts tlast)

### push_bubble

    // Push a bubble cycle onto the AXI-Stream bus

### pull_word

    // Wait for a sample to be transferred on the AXI Stream
    // bus and return the data and last
    // Args:
    // - word: The data pulled from the bus
    // - eop: End of packet (tlast)

### wait_for_bubble

    // Wait for a bubble cycle on the AXI Stream bus

### wait_for_pkt

    // Wait for a packet to finish on the bus

### push_rand_pkt

    // Push a packet with random data onto to the AXI Stream bus
    // Args:
    // - num_samps: Packet size.

### push_ramp_pkt

    // Push a packet with a ramp on to the AXI Stream bus
    // Args:
    // - num_samps: Packet size.
    // - ramp_start: Start value for the ramp
    // - ramp_inc: Increment per clock cycle

# Compressed VITA (sim_chdr_lib.vh)

Note: This section describes legacy CHDR in 3.x and earlier. As of UHD 4.0, the CHDR protocol and format has changed.

Defines cvita_stream_t, an AXI Stream bus interface that implements the CHDR protocol and several tasks to send and receive data on the bus.

## CHDR

    typedef enum logic [1:0] {
      DATA=2'b00, FC=2'b01, CMD=2'b10, RESP=2'b11
    } cvita_pkt_t;

    typedef struct packed {
      logic [31:0]  sid;
      logic [15:0]  length;
      logic [11:0]  seqno;
      logic         eob;
      logic         has_time;
      cvita_pkt_t   pkt_type;
      logic [63:0]  timestamp;
    } cvita_hdr_t;

### Operations

- flatten_chdr_no_ts: Flatten header struct to a 64-bit bus. No timestamp.
- unflatten_chdr_no_ts: Decode a 64-bit header and populate the cvita_hdr_t struct. No timestamp.
- unflatten_chdr: Decode a 64-bit header and populate the cvita_hdr_t struct. Timestamp supported.

## CVITA Stream Type

### Definition

    interface cvita_stream_t (input clk);
      axis_t #(.DWIDTH(64)) axis (.clk(clk));

### push_hdr

    // Push a CVITA header into the stream
    // Args:
    // - hdr: The header to push

### push_data

    // Push a word onto the AXI-Stream bus and wait for it to transfer
    // Args:
    // - word: The data to push onto the bus
    // - eop: End of packet (asserts tlast)

### push_bubble

    // Push a bubble cycle on the AXI-Stream bus

### pull_word

    // Wait for a sample to be transferred on the AXI Stream
    // bus and return the data and last
    // Args:
    // - word: The data pulled from the bus
    // - eop: End of packet (tlast)

### wait_for_bubble

    // Wait for a bubble cycle on the AXI Stream bus

### wait_for_pkt

    // Wait for a packet to finish on the bus

### wait_for_pkt_get_info

    // Wait for a packet to finish on the bus and extract the header and payload statistics.

    typedef struct packed {
      logic [31:0]  count;
      logic [63:0]  sum;
      logic [63:0]  min;
      logic [63:0]  max;
      logic [63:0]  crc;
    } cvita_stats_t;

### push_rand_pkt

    // Push a packet with random data onto to the AXI Stream bus
    // Args:
    // - num_samps: Packet size.
    // - hdr: Header to attach to packet (length will be ignored)
    // - timestamp: Optional timestamp

### push_ramp_pkt

    // Push a packet with a ramp on to the AXI Stream bus
    // Args:
    // - num_samps: Packet size.
    // - ramp_start: Start value for the ramp
    // - ramp_inc: Increment per clock cycle
    // - hdr: Header to attach to packet (length will be ignored)
    // - timestamp: Optional timestamp

# Memory Mapped AXI4 (sim_axi4_lib.vh)

Defines the following interfaces to group signals in the AXI4 bus. WIP: No functions or tasks implemented yet.

### Address

    interface axi4_addr_t #(parameter AWIDTH=32, parameter IDWIDTH=4)
                           (input clk);

      logic [IDWIDTH-1:0] id;
      logic [AWIDTH-1:0]  addr;
      logic [7:0]         len;
      logic [2:0]         size;
      logic [1:0]         burst;
      logic               lock;
      logic [3:0]         cache;
      logic [2:0]         prot;
      logic [3:0]         qos;
      logic [3:0]         region;
      logic               user;
      logic               valid;
      logic               ready;

      modport master (output id,addr,len,size,burst,lock,cache,prot,qos,valid, input ready);
      modport slave (input id,addr,len,size,burst,lock,cache,prot,qos,valid, output ready);

    endinterface

### Write Data

    interface axi4_wdata_t #(parameter DWIDTH=64)
                           (input clk);

      logic [DWIDTH-1:0]      data;
      logic [(DWIDTH/8)-1:0]  strb;
      logic                   last;
      logic                   user;
      logic                   valid;
      logic                   ready;

      modport master(output data,strb,last,valid, input ready);
      modport slave(input data,strb,last,valid, output ready);

    endinterface

### Write Response

    interface axi4_resp_t #(parameter IDWIDTH=4)
                           (input clk);

      logic               ready;
      logic [IDWIDTH-1:0] id;
      logic [1:0]         resp;
      logic               user;
      logic               valid;

      modport master(output ready, input id,resp,valid);
      modport slave(input ready, output id,resp,valid);

    endinterface

### Read Data

    interface axi4_rdata_t #(parameter DWIDTH=64, parameter IDWIDTH=4)
                           (input clk);

      logic               ready;
      logic [IDWIDTH-1:0] id;
      logic [DWIDTH-1:0]  data;
      logic [1:0]         resp;
      logic               user;
      logic               last;
      logic               valid;

      modport master(output ready, input id,data,resp,last,valid);
      modport slave(input ready, output id,data,resp,last,valid);

    endinterface

### Meta: AXI4 Writer

    interface axi4_wr_t #(parameter DWIDTH=64, parameter AWIDTH=32, parameter IDWIDTH=4)
                         (input clk);

      axi4_addr_t  #(.AWIDTH(AWIDTH), .IDWIDTH(IDWIDTH)) addr (.clk(clk));
      axi4_wdata_t #(.DWIDTH(DWIDTH))                    data (.clk(clk));
      axi4_resp_t  #(.IDWIDTH(IDWIDTH))                  resp (.clk(clk));

      modport master(output addr, output data, input resp);
      modport slave(input addr, input data, output resp);

    endinterface

### Meta: AXI4 Reader

    interface axi4_rd_t #(parameter DWIDTH=64, parameter AWIDTH=32, parameter IDWIDTH=4)
                         (input clk);

      axi4_addr_t  #(.AWIDTH(AWIDTH), .IDWIDTH(IDWIDTH)) addr (.clk(clk));
      axi4_rdata_t #(.DWIDTH(DWIDTH), .IDWIDTH(IDWIDTH)) data (.clk(clk));

      modport master(output addr, output data);
      modport slave(input addr, input data);

    endinterface